Graphene, an allotrope of carbon, is an intriguing material because it has potentially influential properties including high electrical conductivity and zero band gap on water splitting. ...Nanostructured hematite (Fe2O3) has been reported as a benchmark catalyst for investigating solar water splitting. In this study, we aim to understand the role of graphene as an underlayer material of hematite using density functional theory+U methodology. To understand the effect of graphene substrate on hematite's catalytic efficiency, we consider pristine graphene as well as graphene with defects (carbon vacancies in different positions and concentrations). Overpotential is found to be reduced for graphene supported hematite as compared to stand-alone hematite. Charge density difference analysis confirms more charge delocalization when carbon vacancies is present in the system. This observation is supported by smaller magnetization values and net Bader charge of the active site. Furthermore, graphene plays an important role in reducing the band gap significantly which is beneficial for catalytic efficiency. In particular, hematite supported by graphene having vacancies had nearly zero band gap which is expected to help charge carrier to be transported to the surface. We have calculated the cumulative probability of a charge to reach hematite's surface using a wave propagation simulator. Graphene supported hematite has higher cumulative probability of charge transfer than bare hematite. Graphene supported hematite having carbon vacancies in graphene shows higher cumulative probability than its pristine counterpart. These indicatives for improved carrier transport and catalysis are beneficial for water splitting. These observations also support the previously reported experimental electron impedance spectroscopy (EIS) results where graphene overlayered hematite has reported to have lower band gap, higher photocurrent density and promotable solar-driven water oxidation reaction.
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•Graphene underlayer helps to reduce the overpotential of nanostructured hematite.•Graphene plays a key role to reduce band gap significantly benefitting catalysis.•Vacancies in graphene lead to more charge delocalization.•Carbon vacancies increase the probability of a charge to reach hematite's surface.
Single Atom Catalysts (SACs) are a new frontier in catalysis, merging the positive aspects of both homogeneous and heterogenous catalysts. CO2 electrochemical reduction is a key reaction for the ...energy transition. In this work, we investigate the role of the local coordination on the activation of CO2 on SACs, by means of density functional theory (DFT) calculations. We scrutinize 20 transitional metal atoms embedded in a graphene support. The results indicate that the local coordination has a critical role both to the binding energy of the metal to the support and the activation of CO2. The role of the environment around the active site is as important as the nature of the metal atom. At the same time, the stability of reaction intermediates strongly depends on the local coordination. In some cases, the relative stability of the intermediates changes as function of the environment, affecting the selectivity of the reaction. This study provides evidence of the importance of the local coordination in single-atom catalysis, a crucial aspect if one is interested in providing a rationale to the reactivity, or in predicting novel catalysts.
Novel functional materials, namely TPI-TAZ-ISA, NADPI-TAZ-ISA, ADPI-TAZ-ISA, and DMAPDPI-TAZ-ISA, were synthesized utilizing click chemical reactions and subjected to thorough characterization. The ...optical properties of these organic materials, TPI-TAZ-ISA, NADPI-TAZ-ISA, ADPI-TAZ-ISA, and DMAPDPI-TAZ-ISA, were investigated in various solvent environments. Notably, ADPI-TAZ-ISA exhibited a maximum absorption wavelength of 390 nm attributed to π – π* electronic transitions, primarily originating from the fluorophore group, while displaying a blue fluorescence at 465 nm. A comprehensive investigation combining experimental and theoretical approaches was conducted for these compounds, revealing a non-planar molecular structure and theoretical energy band gaps ranging from 4.10 to 4.73 eV. DFT studies demonstrated well-defined spatial separation of the HOMO and LUMO for all compounds in the ground state (S0). NTO studies further elucidated the spatial separation of the HONTO and LUNTO for DMAPDPI-TAZ-ISA at the excited state (S2), corroborated by CDD, hole and electron contributions, and the overlap of hole and electron densities. These findings hold promise for the development of novel luminescent materials. Moreover, on-going research is exploring the integration of ISA to enhance the functionality of these materials further.
•The synthesis and characterization of TPI-TAZ-ISA, NADPI-TAZ-ISA, ADPI-TAZ-ISA, and DMAPDPI-TAZ-ISA compounds are presented.•Absorption and emission properties are determined through experimental and DFT methods.•The optical characteristics of compounds TPI-TAZ-ISA, NADPI-TAZ-ISA, ADPI-TAZ-ISA, and DMAPDPI-TAZ-ISA are primarily attributed to local π–π* transitions.•Comprehensive analyses utilizing DFT and TD-DFT are conducted for the synthesized compounds.•ISA is identified as a potential acceptor, facilitating the creation of desired blue emissive optoelectronic materials.
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The vicinal effect on chlorination reactions of diols was investigated by computational methods. Applying density functional theory (DFT) combined with polarizable continuum model (PCM) and explicit ...solvent molecules, we demonstrated the effect of hydration on the leaving and vicinal hydroxyl group in SN2 reactions of selected alcohols. Our results point out to the importance of intermolecular hydrogen bonds as a stabilizing factor in reaction pre-complexes and alcohols with vicinal hydroxyl groups, highlighting the importance of solute-solvent network formation. This indicates the significance of adequately describing the solvent in the study of reaction mechanisms, in special when the interaction with solute molecules and ions are strong. Also, we found a “vinical effect” on the reactivity, in other words, alcohols with vicinal hydroxyl groups exhibit higher activation energies when compared to related monoalcohols. Moreover, 1,3-propanediol and 1,3-butanediol present the highest activation energies.
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•The microsolvation allows capturing important effects for halogenation reactions.•Adjacent hydroxyls contribute to the solvation network formation.•The activation energy increases in respect to the number of water molecules.•The formation of a solvation network stabilizes the pre-complex.
The adsorption and sensing capabilities of CO and NO on pristine and metal-decorated (8,0) SWCNT were analyzed by DFT. Both gases cause a slight deformation of the nanotube curvature in the direction ...of molecular adsorption. The molecule's adsorption and sensing performance are enhanced with the transition metal (Sc, Cr, Fe, and Ni) decoration on SWCNT. Decorated nanotubes are suitable for high-temperature sensors. According to relative energies for NO, the operational range is 900–1200 K. For CO/Cr- and Sc-SWCNT between 100 and 200 K and close to 550 K in the cases of decoration with Fe and Ni. From the recovery time analysis, the metal-decorated materials exhibit better performance at high temperatures and low pressures for NO compared to CO. Changes in magnetic moment suggest that Cr-decorated SWCNT could serve as a magnetic sensor for both molecules.
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•The pristine CNT is more reactive to NO than CO.•The transition metal (TM) doping enhances the adsorption energy and sensing performance for NO and CO.•TM-doped SWCNTs are better for sensing NO at high temperature and low pressure.•Recovery time shows that the best sensors for NO are Cr and Ni decorated CNT.•At room temperature, TM-SWCNTs could be effective for absorbing material to clean both gases.
•C4-substituted coumarins (X= –CH3, –OH, –NH2, –CONH2, –CHO, and –NO2) are characterized using UV–vis and IR techniques.•Identifying planar geometry for C4-substituted coumarins, except -NO2 ...substitution.•Acceptor functional groups reduce the energy of lowest 2P-actived state and enhances TPA cross-section.•Identification of maximum TPA cross-section of 18.82 GM (at 1.36 eV) in aqueous solution.•Polar solvents, like water, can effectively enhance the TPA cross-section.
The versatile applications of coumarin derivatives in materials processing, fluorescence imaging, data storage, and photodynamic therapy have sparked considerable interest in scientific community. In this research paper, we explore the UV–vis spectra, IR spectra, and two photon absorption (TPA) characteristics of biological active coumarin derivatives under the influence of electron withdrawing (specifically X = CONH2, CHO, and NO2) and electron donating (X= -CH3, -OH, -NH2) functional groups at C-4 position. To delve into the absorption spectra, we employ time-dependent density functional theory calculations. Results revealed that acceptor functional groups (specifically R = CONH2, CHO, and NO2) not only lower the energy of the lowest two photon active state but also increase the corresponding TPA cross-section. Furthermore, using the Conductor-like Polarizable Continuum Model (CPCM), the influence of solvent polarity on C-4 substituted coumarin derivative was also investigated. Our findings effectively capture how substitutions and solvents impact the nonlinear optical response in coumarins, as evidenced by the measurement of the two-photon absorption cross-section (σTPA). This study offers valuable insights for identifying and designing novel coumarin derivatives with C4 substitutions, unlocking new and intriguing possibilities for their practical applications.
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Different concentrations of zirconium with a fixed quantity (4 wt%) of chitosan (CS) doped nickel cobaltite (NiCo2O4) nanorods were synthesized using a co-precipitation approach. This cutting-edge ...research explores the cooperative effect of Zr-doped CS-NiCo2O4 to degrade the Eriochrome black T (EBT) and investigates potent antibacterial activity against Staphylococcus aureus (S. aureus). Advanced characterization techniques were conducted to analyze structural textures, morphological analysis, and optical characteristics of synthesized materials. XRD pattern unveiled the spinal cubic structure of NiCo2O4, incorporating Zr and CS peak shifted to a lower 2θ value. UV–Vis spectroscopy revealed the absorption range increased with CS and the same trend was observed upon Zr, showing a decrease in bandgap energy (Eg) from 2.55 to 2.4 eV. The optimal photocatalytic efficacy of doped NiCo2O4 within the basic medium was around 96.26 %, and bactericidal efficacy was examined against S. aureus, revealing a remarkable inhibition zone (5.95 mm).
In this study, we have investigated the electronic , structural, elastic, optical and thermodynamic properties of the copper-based ternary semiconductors, that is, KCuZ (Z= Te, Se). The properties of ...these materials have been precisely determined based on first-principle calculations. The lattice constants, bulk modulus and equilibrium total energies were obtained from Murnaghan equation of state and have a good agreement with other theoretical and experimental methods. The absorption spectra was analyzed to determine the active window of electromagnetic spectrum of the compounds. The elastic constants of these materials were elucidated and hence provided vital information about the material’s ability to withstand external stress. The results indicate that the materials conform to the stability criteria with brittle behavior and anisotropic nature in the HCP structure. The electronic band structures and density of states were computed and the results obtained suggests that the these materials have a band gap of 1.25 eV and 1.1 eV for KCuTe and KCuSe respectively and therefore they are suitable for photovoltaic applications. The materials are also found to posses desirable optical properties i.e. the materials have a good optical absorption since highest absorption peaks occur within the UV region, small reflectivity and high dielectric constant indicating that the materials is suitable for use as solar absorbers.
•KCuTe and KCuSe are both hexagonal in nature and belong to space group P63/mmc.•KCuTe and KCuSe structures are mechanically and thermodynamically stable.•All the two compounds are brittle.•Band gaps of 1.1 eV for KCuSe and 1.25 eV fo KCuTe.
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